Mayor Rahm Emanuel and Police Supt. Eddie Johnson on Tuesday bemoaned the fights that forced the United Center to close, canceling the championship game of a basketball league intended to keep teenagers off the streets in the summer.

The pandemonium — some captured on cellphone video — prevented neighborhood teams made up of players from two of Chicago’s top high school basketball teams — Orr Academy and Curie Metropolitan — from squaring off in a title game.

As upsetting to Emanuel and Johnson as the ugly scene outside the United Center was the fact that the league itself was supposed to provide a constructive alternative to the lure of gang activity.

HOOPS: United Center closed after fights break out at youth basketball game

That the showcase game would dissolve into fights and pandemonium that forced the United Center to close on Monday night and cancel the championship game was a cause for sadness for both men.

“The whole purpose was for athletics and what I would call friendly competition. And the fans should not be involved in anything that’s disruptive to that,” Emanuel said.

“It’s unfortunate that … the game had to get canceled and the kids missed out,” he added. “Thank God nobody was seriously hurt.”

Johnson called the 5:09 p.m. cancellation by apparently overwhelmed United Center security “unfortunate” to say the least.

Free tickets were provided to the event, which is normally held at West Side high schools near the United Center. Security had to close the doors after nearly 10,000 people showed up.

Fans who were kicked out were met with angry fans outside who were unable to get in, according to a source inside the United Center. Orr coach Lou Adams described the scene as a “madhouse.” Adams told the Chicago Sun-Times his team made it out safe, and he’s resolved never to take his team back.

“It’s just ridiculous that kids can’t go out, enjoy themselves and have a good time without some people causing problems,” Johnson said Tuesday.

“It’s frustrating. The whole point of that event was to keep kids safe and it turned into what it did. It’s unacceptable. … That just goes to show you that you have to have security in place in the event that those types of things happen if you’re gonna invite that many young people. We’ll be talking to the sponsors to make sure their security plans are on point next time,” he said.

United Center security wasn’t Johnson’s only concern.

So was the apparent security lapse that allowed a man to smuggle a knife — subsequently used to stab a man — into a punk concert last week at Northerly Island.

“We’re talking to those private security folks. Clearly, they can do things better. And I’m sure that they will,” Johnson said, referring to Monterrey Security, the firm hired by Live Nation to handle security at Huntington Bank Pavillion.

At minimum, Monterrey guards are supposed to use metal detector wands to screen concert-goers before they enter the popular concert venue.

“Any time you have something like that happen, it begs the question, ‘What can we do better?’ Knives are small weapons,” Johnson said. “But I would just suggest to them to just be more thorough when they screen people.”

Thomas Christensen, 34, faces one felony count of aggravated battery with the use of a deadly weapon and one misdemeanor count of battery in connection with the stabbing. He had argued with a 29-year-old man and 34-year-old woman at a bar inside the pavilion during a concert, then pulled a knife and stabbed the man in the neck and face, police said.

Chicago Police officers and a protester outside Belmont and Western branch courthouse Tuesday afternoon. | Andy Grimm for the Sun-Times

On Tuesday afternoon, police arrested three protesters who were among about 70 demonstrators who rallied outside the Cook County Court branch at Belmont and Western avenues, where Christensen appeared for a hearing. The marchers, organized by local anti-fascist groups, blocked traffic at the intersection until dispersed by police.

Police jostled with demonstrators who refused to leave the street and move onto the sidewalk, police at the scene said. About 20 minutes later, a third man was grappled down by officers in the courthouse parking lot after the man attempted to photograph a vehicle that had run into a protester, according to a fellow protester.

Contributing: Andy Grimm